Recently, regarding recovery of carbon dioxide, carbon dioxide capture and storage techniques have attracted attention as effective countermeasures to the problem of global warming which is concerned on a global scale. Particularly, there has been considered a method for recovering carbon dioxide with an aqueous solution for a thermal power station and a process emission gas.
As such a carbon dioxide recovery apparatus, there has been known one which is provided with: an absorption tower which causes a carbon dioxide-containing gas to be absorbed into an absorbing liquid and generates a rich liquid; a desorption tower which heats the rich liquid discharged from the absorption tower to desorb carbon dioxide with steam and, thus, to separate carbon dioxide-containing steam, and returns a generated lean liquid to the absorption tower; a first heat exchanger through which the lean liquid supplied from the desorption tower to the absorption tower passes; a second heat exchanger through which the carbon dioxide-containing steam separated in the desorption tower passes; and a flow divider which distributes the rich liquid discharged from the absorption tower to the first and second heat exchangers. In this carbon dioxide recovery apparatus, after the rich liquids introduced into the first and second heat exchangers exchange the heat with the lean liquid and the carbon dioxide-containing steam, respectively, the rich liquid is supplied to the desorption tower.
In the above conventional carbon dioxide recovery apparatus, thermal energy of the carbon dioxide-containing steam separated in the desorption tower can be recovered in the second heat exchanger by the distributed rich liquid. However, the flow rate of the rich liquid passing through the first heat exchanger is reduced to facilitate increase in temperature, and consequently, a temperature difference from the lean liquid as a high-temperature side fluid is reduced, whereby there is a problem that an amount of thermal energy recovered from the lean liquid at this site is reduced more than in a case where the rich liquid is not divided. This tendency becomes more notable when the performance of the first heat exchanger is improved by measures such as increasing a heat transfer area to reduce the amount of steam consumption in the carbon dioxide recovery apparatus.